Effects of Age Related Degeneration on Cervical Spine Mechanics

The average age of people suffering spinal cord injuries (SCIs) is shifting toward an older population, frequently occurring in the spondylotic (degenerated) cervical spine, due to low energy impacts. Since canal stenosis (narrowing) is a common feature of a spondylotic cervical spine, flexion or extension of such a spine can compress the spinal cord. This thesis involves two studies investigating the effects of spondylosis on the kinematics of the cervical spine and on compression of the spinal cord during spine motion.

The first study developed and evaluated an image analysis technique that measures a new combination of degenerative and kinematic continuous, quantitative variables in cervical spine sagittal plane flexion-extension image pairs. This technique, evaluated using plane X-ray, effectively quantified angular range of motion, anterior-posterior (AP) translation, intervertebral disc height, pincer spinal canal diameter, and osteophyte length. The angular accuracy and linear precision were found to be ±1.3° and approximately ±0.6mm, respectively. This compared well to previous studies and is adequate for potential clinical applications.

The second study quantified the effect of increasing anterior canal stenosis on spinal cord compression during spine motion. This study used a whole porcine cadaveric cervical spine, a radio-opaque surrogate spinal cord, and an artificial osteophyte. The spine was imaged by sagittal plane X-ray during quasistatic pure moment flexionextension bending. This study demonstrated that the cadaveric model could simulate the typical spondylotic SCI mechanisms in both flexion (bowstring stretching) and extension (pincer). Spinal cord AP diameter could be measured accurately within ±0.25mm and cord diameter differences could be measured within ±0.5mm. Cord compression due to the artificial osteophyte increased with increased canal stenosis, but never exceeded 1mm.

The image analysis techniques developed in the first study and results of future studies based on these techniques may be used to improve cadaveric modelling of SCI due to low energy impacts in the presence of age-related spine degeneration. Improved understanding of injury mechanisms may aid clinical intervention to both prevent and treat SCI in the presence of age-related spine degeneration.

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Year

Entry

2004

Goertzen DJ, Lane C, Oxland TR. Neutral zone and range of motion in the spine are greater with stepwise loading than with a continuous loading protocol: an in vitro porcine investigation. J Biomech. February 2004;37(2):257-261.

1988

Kearney PA, Ridella SA, Viano DC, Anderson TE. Interaction of contact velocity and cord compression in determining the severity of spinal cord injury. J Neurotrauma. 1988;5(3):187-208.

2001

Panjabi MM, Miura T, Cripton PA, Wang J-L, Nain AS, DuBois C. Development of a system for in vitro neck muscle force replication in whole cervical spine experiments. Spine. October 15, 2001;26(20):2214-2219.

2000

Bogduk N, Mercer S. Biomechanics of the cervical spine, I: normal kinematics. Clin Biomech (Bristol, Avon). November 2000;15(9):633-648.

2001

Bogduk N, Yoganandan N. Biomechanics of the cervical spine, III: minor injuries. Clin Biomech (Bristol, Avon). May 2001;16(4):267-275.